MakeHuman "MHX FK/IK switch" missing
I have Blender 2.79 and MHX2, for those figuring this out lately.
I did not access this through the properties menu.

I have found that option from the menu option below: View->Tool Shelf

OR

Pressing T.

After that, a panel will appear on the left.
Under the MHX2 Runtime you will see the submenu FK/IK Switch.